Multiview display device

ABSTRACT

The invention provides an autostereoscopic display device having an adjuster for adjusting the direction of a light beam (5). The adjuster (1) has an off-state and on-state and comprises a stack (10) of layers. The stack (10) comprises a first solid material layer (100) having a first optic axis (111), a second solid material layer (200) having a second optic axis (211), and switchable birefringent twisted nematic liquid crystal material (30) or chiral nematic liquid crystal material. Further, the stack includes a first interface (130) between the first solid material layer (100) and birefringent material (30) and a second interface (230) between the second solid material layer (200) and birefringent material (30). In the off-state, the birefringent material (30) at the first interface (130) is configured to have an optic axis parallel to the first optic axis (111) and the birefringent material (30) at the second interface (230) is configured to have an optic axis parallel to the second optic axis (211). In the on-state, the birefringent material (30) at the first interface (130) is configured to have an optic axis perpendicular to the first optic axis (111) and the birefringent material (30) at the second interface (230) is configured to have an optic axis perpendicular to the second optic axis (211).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 15/258,016 filed onSep. 7, 2016 which is a continuation of U.S. Pat. No. 9,448,459 filedSep. 20, 2016 which is a U.S. national phase application ofInternational Application No. PCT/IB2010/054407 filed Sep. 30, 2010which claims the benefit of EP Applications Serial No. 09174563.8 filedOct. 30, 2009 and EP10163323.8 filed May 19, 2010 all of which areincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to Multi-view displays such as autostereoscopic ordual-view displays, which use an adjuster for adjusting the direction oflight beams from a display panel.

BACKGROUND OF THE INVENTION

US 2007/0008617 discloses a 2D/3D switchable autostereoscopic displaydevice in which a switchable lenticular arrangement has two lens sheets,with first and second electro-optical mediums between the sheets, with ahalf wave plate between.

SUMMARY OF THE INVENTION

According to the invention, there is provided a multi-view displaydevice as defined in the independent claims. The dependent claimsprovide advantageous embodiments.

In this arrangement, the adjuster is configured to be able to adjust thedirection of the beam of light (“light beam” or “beam”) generated by alight source. In general, the adjuster is arranged to intercept the beamof light (when the light source is switched on). In at least one of thestates, the adjuster is at least partially transmissive for at leastpart of the light generated by the light source to which the adjuster isarranged. Preferably, in both the on and off states, the adjuster is atleast partially transmissive for at least part of the light generated bythe light source to which the adjuster is arranged. The phrase “foradjusting the direction of a light beam” especially indicates that whenthe adjuster is switched on, the light beam adjusts the beam of light.When the adjuster is switched off, the light beam may pass the adjusterin an embodiment substantially unchanged.

The phrase “having an off-state and an on-state” indicates that theadjuster is configured to have a least two states, which are specifiedherein further. In the off-state, the light beam may pass the adjusterwithout being substantially influenced by the adjuster. In the on-state,the beam is at least partly manipulated by the adjuster. Note that theterm “on-state” may refer to a plurality of on-states. Depending uponthe conditions (such as voltage) applied to the birefringent material,different on-states, and thus different manipulations of the light beammay be obtained. In this way, a user may manipulate the beam dependentupon the desires of the user. Further herein, the “on-state” is used fora specific state that at least may be provided by the adjuster whenswitched on. Thus, intermediate states between the off-state and thespecifically defined on-state may also be selectable for the adjuster.

The term “stack of layers” refers to substantially adjacent layers (seefurther also below). This does not exclude that the interfaces betweentwo adjacent layers may have one or more curves or one or more angles.Especially, the interfaces between the solid birefringent material layerand the switchable birefringent material may comprise one or moremicrostructures such as prism structures. Preferably the interfaces arenon-planar. The external faces of the first and the second materiallayers are however preferably arranged substantially parallel. Thesefaces are preferably planer, whereas the layers at the interfaces withthe switchable birefringent material are (thus) preferably substantiallynon-planar and comprise one or more microstructures.

The first interface and the second interface preferably have the shapeof a plurality of lenses or prisms. The lenses may be directly adjacent,but there may also be a non-zero distance between the lenses or prisms.Preferably, the shapes of the lenses or prisms are substantial mirrorimages of each other.

Hence, preferably, in an embodiment the first interface and the secondinterface have the shape of a plurality of 1D lenses.

The arrangement of lenses is used to define a switchable lenticularimaging arrangement of a multi-view display device, such as anautostereoscopic or dual-view display device. For the autostereoscopicdisplay preferably an array of lenses is used as this enables more than3 views.

The multi-view display device may be an autostereoscopic display device.Such a device is capable of providing at least one viewer with a threedimensional (3D) image. In this case in the on state, the multi-viewmode is a 3D mode, while in the off state the single view mode may be a2D mode. Alternatively, the multi-view display device may be a dual-viewdisplay device. In this case in the on state the multi-view mode is forproviding at least two different 2D images to at least two viewers. Thuse.g. the dual-view display may be in effect a triple view displaycapable of providing three different 2D images to three viewers. Thesingle view mode may be for providing a single two-dimensional image.

The term image comprises still image, static image or video display ofany kind.

This switchable lenticular lens arrangement is suitable for use with anOLED display panel which generates the light beams. This has unpolarizedlight output, but the adjuster design does not require a polarized lightinput. It may operate without light of the OLED display panel being lostor having to be discarded. In general display panels that provideunpolarized light may be used without loss of effect.

The first and the second solid material layers preferably comprise solidmaterials that are birefringent. The term “solid birefringent material”relates to a birefringent material of which the optic axis alignment isnot variable, as is the case for the switchable birefringent material.Birefringence, or double refraction, is the decomposition of a ray oflight into two rays (the ordinary ray and the extraordinary ray) when itpasses through certain types of material depending on the polarizationof the light. This effect can occur only if the structure of thematerial is anisotropic (directionally dependent). If the material has asingle axis of anisotropy or optic axis (i.e. it is uniaxial),birefringence can be formalized by assigning two different refractiveindices to the material that are commonly called ordinary refractiveindex and extra-ordinary refractive index.

The term optic axis is known in the art and relate to a direction at aposition in an uniaxial medium such that all ordinary rays passing thatposition have polarization that is perpendicular to it. Often, the opticaxis is close to the director of the molecules in case of a liquidcrystal. See further, Hecht (Optics, 4^(th) edition, E. Hecht,Addison-Wesley).

Examples of suitable materials for the first and the second materiallayers are for instance based on LC's such as RMM34c or RMM257 LC fromMerck, that are included in a photopolymerized system. Such systems arefor instance described in WO2004059565 and are known to the personskilled in the art.

In the “off-state” for each interface the media on both sides of theinterface may give rise to a refractive index that is substantially thesame on both sides of the interface for unpolarized light being alignedto a normal of the stack (off-state).

The switchable (birefringent) medium at each of the two interfaces canbe switched to a state called “on-state” where for the first interfacethe media on both sides of the interface may give rise to a refractiveindex that is substantially the same on both sides of the interface forlight being aligned to a normal of the stack and having a polarizationin a second direction being either aligned or perpendicular to the firstdirection and give rise to a refractive index that is substantiallydifferent on both sides of the interface for light being aligned to anormal of the stack and having a polarization in a direction that isperpendicular to the second direction, and where for the secondinterface the media on both sides of the interface give rise to arefractive index that is substantially the same on both sides of theinterface for light being aligned to a normal of the stack and having apolarization in a third direction being either aligned or perpendicularto the first direction and give rise to a refractive index that issubstantially different on both sides of the interface for light beingaligned to a normal of the stack and having a polarization in adirection that is perpendicular to the third direction.

The stack comprises a stack of the first solid material layer, a layerof switchable birefringent material, and the second solid materiallayer. The first optic axis and the second optic axis are preferablyperpendicular. Such adjuster essentially consists of three layers,wherein the first and second solid material layers sandwich theswitchable birefringent material. The switchable birefringent comprisestwisted nematic liquid crystal or chiral nematic liquid crystalmaterial. Further, the first optic axis and the second optic axis may beoriented in a plane of the stack.

This arrangement provides a simple construction and requires only oneset of electrodes for switching. The use of a single switchable layerenables a thin construction, which means that the differentpolarizations experience reduced path differences resulting from thedifferent depths at which refraction takes place.

In the off-state, the optic axis of the switchable birefringent materialat the first interface is perpendicular to the optic axis of the sameswitchable material at the second interface. By for instance usingtwisted nematic liquid crystal, a twist of substantially 90° may beimposed to the optic axis of the switchable material over the materiallayer.

In the on-state, the optic axis (or optic axes) of the birefringentmaterial in the layer of switchable birefringent material changes to astate wherein the optic axis is perpendicular to both the optic axis ifthe first solid material layer and the optic axis of the second materiallayer. In the on-state, the optic axes within the switchable materialare substantially all aligned. An advantage of this embodiment is thatrelatively simple adjuster can be obtained with three layers only.

As known in the art, for alignment of liquid crystals one may usestandard polyimide layers that are rubbed for orienting the LC close tothe surface. Electric fields can be used for imposing a secondorientation of the LC. For generating electric fields (transparentindium tin oxide (ITO) electrodes may be applied. Hence, the term “stackof layers” refers to substantially adjacent layers where between twosubstantially adjacent layers also an ITO layer and/or a polyimide layerare present. Herein, the adjuster is especially described with referenceto the three or more layers that are essential for the adjuster, i.e.the first solid material layer, the second solid material layer and oneor more layers of switchable birefringent material.

Unless indicated otherwise, and where applicable and technicallyfeasible, the phrase “selected from the group consisting” a number ofelements may also refer to a combination of two or more of theenumerated elements. Terms like “below”, “above”, “top”, and “bottom”relate to positions or arrangements of items which would be obtainedwhen the lighting system is arranged substantially flat to, particularlybelow, a substantially horizontal surface with the lighting systembottom face substantially parallel to the substantially horizontalsurface and facing away from the ceiling into the room. However, thisdoes not exclude the use of the lighting system in other arrangements,such as against a wall, or in other (e.g. vertical) arrangements.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 schematically depicts some principles of the invention;

FIGS. 2a-2b schematically depict an embodiment of the adjuster in the“off” and “on” state—this embodiment is used in the display of theinvention;

FIGS. 3a-3b schematically depict another embodiment of the adjuster inthe “off” and “on” state;

FIGS. 4a-4b schematically depict yet another embodiment of the adjusterin the “off” and “on” state;

FIGS. 5a-5b schematically depict embodiments of micro-structuredinterfaces;

FIGS. 6a-6c schematically depict embodiments of optical devicescomprising the adjuster;

FIG. 7 is used to explain how a switchable lens arrangement can be usedfor providing a switchable 2D/3D display;

FIG. 8 shows a first example of optical arrangement used in anautostereoscopic display in the 2D mode;

FIG. 9 shows the optical arrangement of FIG. 8 in the 3D mode;

FIG. 10 shows a first example of optical arrangement of the inventionfor an autostereoscopic display in the 2D mode;

FIG. 11 shows the optical arrangement of FIG. 10 in the 3D mode;

FIG. 12 shows a second example of optical arrangement of the inventionfor an autostereoscopic display in the 2D mode; and

FIG. 13 shows the optical arrangement of FIG. 12 in the 3D mode.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Before describing the invention, some designs and uses of opticaladjuster as developed (but not yet published) by the applicant willfirst be described.

FIG. 1 schematically depicts an adjuster 1 for adjusting the directionof a light beam 5. The adjuster 1 comprises a stack 10 of layers. Thestack 10 comprises a first solid material layer 100 having a first opticaxis (not depicted, see FIGS. 2a-4b ), a second solid material layer 200having a second optic axis (not depicted, see FIGS. 2a-4b ), andswitchable birefringent material 30. The switchable birefringentmaterial may be arranged in a single layer or in separate layers (seebelow).

For the sake of understanding, polyimide layers and electrode layerssuch as ITO layers are not drawn in the Figs. Those features are knownto the person skilled in the art. The term “adjacent” herein may thus insome embodiments mean that between at least part of adjacent items, forinstance a polyimide layer and/or (transparent) ITO layer is present.

The stack further comprises a first interface 130 between the firstsolid material layer 100 and birefringent material 30 and a secondinterface 230 between the second solid material layer 200 andbirefringent material 30.

The materials of the first material layer 100 and the second materiallayer 200 as well as the switchable birefringent material are selectedand configures that (a) in the off-state, the birefringent material 30at the first interface 130 is configured to have an optic axis parallelto the first optic axis and the birefringent material 30 at the secondinterface 230 is configured to have an optic axis parallel to the secondoptic axis; and (2) in the on-state, the birefringent material 30 at thefirst interface 130 is configured to have an optic axis perpendicular tothe first optic axis and the birefringent material 30 at the secondinterface 230 is configured to have an optic axis perpendicular to thesecond optic axis.

The first and the second solid material layers 100,200 preferablycomprise solid materials that are birefringent. The switchablebirefringent material is preferably liquid crystal, such as twistednematic liquid crystal or chiral nematic liquid crystal.

Especially, the interfaces 130,230 may comprise one or moremicrostructures (see below). The external faces of the first and thesecond material layers are however preferably arranged substantiallyparallel. These faces are preferably planar, whereas the layers at theinterfaces 130,230 with the switchable birefringent material are (thus)preferably substantially non-planar and comprise one or moremicrostructures (see below).

In a specific embodiment, depicted in FIGS. 2a-2b (“off-state” and“on-state”, respectively), the stack 10 comprises a stack of the firstsolid material layer 100, a layer 300 of switchable birefringentmaterial 30, and the second solid material layer 200. The first opticaxis, indicated with reference 111, and the second optic axis, indicatedwith reference 211, are chosen perpendicular. Such adjuster 1essentially consists of three layers, wherein the first and second solidmaterial layers sandwich the switchable birefringent material.Especially, in such embodiment, the switchable birefringent material 30comprises twisted nematic liquid crystal material, like such as TL213from Merck.

The invention involves the use of this type of adjuster within aswitchable autostereoscopic display device, as explained further below.

In the off-state, the optic axis (or here optic axes because especiallychiral nematic material is applied as switchable birefringent material)of the switchable birefringent material, which optic axis is indicatedwith reference, 311 at the respective interfaces 130 and 230 are alignedparallel with the optic axes 111 and 211 (of the solid materials at theother side of the respective interfaces). Hence, at the interfaces130,230 the optic axes are aligned parallel at both sides of theinterfaces, respectively. The optic axis of the birefringent materiallayer may rotate over 90° to obtain the desired configuration of theoptic axes in relation to the first and second optic axes 111,211 of thefirst and second solid materials 100,200.

The layer thickness of the switchable birefringent layer in thisembodiment, wherein the birefringent material may comprise twistednematic LC, may be in the range of about 40-100 μm, such as about 50 μm.Such thickness may be enough to create a 90°, rotation.

When the adjuster 1 is switched on, the alignment of the optic axis ofthe switchable birefringent material 30 changes, and alignsperpendicular to both the optic axes of the first and second materiallayers, respectively. Here, the optic axis 311 of the birefringentmaterial, through substantially the entire material, is alignedperpendicular to the optic axes 111,211 of the first and second materiallayers.

In a further specific embodiment, depicted in FIGS. 3a-3b (“off-state”and “on-state”, respectively), the stack 10 comprises a stack 10 of:

a first layer 301 of switchable birefringent material 30;

first solid material layer 100;

a second layer 302 of switchable material 30; and

the second solid material layer 200.

The first layer 301 of switchable birefringent material 30 and the firstsolid material layer 100 create first interface 130. The second layer302 of switchable material 30 and the second solid material layer 200create second interface 230. In fact, this stack 10 comprises 2 cells,i.e. the first layer 301 and the first solid material 100, and thesecond layer 302 and the second solid material 200. These two cells maybe arranged adjacent, i.e. first material 100 and second layer 302create a further interface 400. This further interface 400 is preferablyplanar. The optic axis in the respective first and second layers 301,302of switchable birefringent material 30 are indicated with references311(1) and 311(2), respectively.

Here, the first optic axis 111 and the second optic axis 211 in thisembodiment are perpendicular. The optic axis 311(1) (substantially allover the material of the first layer 301 of switchable birefringentmaterial 30) of the first layer 301 is parallel with the first opticaxis 111. The optic axis 311(2) (substantially all over the material ofthe second layer 302 of switchable birefringent material 30) of thesecond layer 302 is parallel with the second optic axis 211.

In the off-state, the optic axis 311(1) and 311(2) at the respectiveinterfaces 130 and 230 are thus aligned parallel with the optic axis 111and 211 of the first solid material layer 100 and the second solidmaterial layer 200, respectively. When the adjuster 1 is switched on,the alignment of the optic axis of the switchable birefringent material30 changes and aligns perpendicular to both the optic axes of the firstand second material layers, respectively, and perpendicular to eachother. Referring to FIG. 3b , the optic axis 311(1) of the first layer301 of switchable birefringent material 30 is perpendicular to the opticaxis 111 of the first solid material layer 100 and perpendicular to theoptic axis 311(2) of the second layer 302 of switchable birefringentmaterial 30. The optic axis 311(2) of the second layer 302 of switchablebirefringent material 30 is perpendicular to the optic axis 211 of thesecond solid material layer 200 and perpendicular to the optic axis311(1) of the first layer 301 of switchable birefringent material 30.

In yet a further specific embodiment, depicted in FIGS. 4a-4b(“off-state” and “on-state”, respectively), the stack 10 comprises astack of the first solid material layer 100;

a first layer 301 of switchable birefringent material 30;

an intermediate layer 500 comprising a polarization rotator, such as atwisted nematic cell;

a second layer 302 of switchable material 30; and

the second solid material layer 200.

The first layer 301 of switchable birefringent material 30 and the firstsolid material layer 100 create first interface 130. The second layer302 of switchable material 30 and the second solid material layer 200create second interface 230.

Here, again, two cells are provided, which cells both comprise aswitchable birefringent material and a (birefringent) solid materiallayer. The optic axes (111/311(1) and 211/311(2)) within the individualcells (100/301 and 200/302, respectively) are aligned parallel. Further,all optic axes may be aligned parallel in the off state.

Between the two cells, the polarization rotator 500 is arranged. Thecells may sandwich the polarization rotator 500. In a specificembodiment, the first layer 301 of switchable birefringent material 30creates an interface 501 with the polarization rotator 500. In a furtherspecific embodiment, the second layer 302 of switchable birefringentmaterial 30 creates an interface 502 with the polarization rotator 500.

In the on-state, the direction of the optic axes of the switchablebirefringent material 30 changes for both the first layer 301 and thesecond layer 302. The optic axes 311(1) and 311(2) swap to aperpendicular state relative to the optic axes 111,211 of the solidmaterial layers 100, 200 respectively. Further, they swap to a statewherein they are mutually parallel. Further, they may swap to a statewherein they are substantially perpendicular to the external face (i.e.substantially parallel to a normal to the stack 1).

FIGS. 5a-5b non-limitingly depict some embodiments of microstructures onthe interfaces 130 and 230. These microstructures are in FIG. 5alens-shaped, and in FIG. 5b sawtooth shaped. Note that preferably, themicrostructures are one-dimensional. Hence, FIGS. 5a /5 b mayschematically depict cross-sections of embodiments of stack 10.

In some of the embodiments (see for instance FIGS. 1-3), the change inrefractive index for the deflected part of the beam passing the firstinterface in the on-state is opposite in sign with respect to the changeof the refractive index of the deflected part of the beam passing thesecond interface. When demanding the same action at each interface(redirection in a certain direction or focusing, for instance) then forsmall differences in index, the shapes of the microstructures maysubstantially be mirror images. One can, however, induce smalldifferences for obtaining an optimal effect. For the embodiment of FIGS.4a-4b , preferably the interfaces do not comprise microstructures.

FIGS. 6a-6b schematically depicts embodiments of an optical device 600comprising the adjuster 1.

The optical device 600 comprises a light source 601 configured togenerate a beam of light 5. The optical device 600 further comprises theadjuster 1 for adjusting the direction of a light beam 5. The opticaldevice 600 may be arranged to generate a single beam of light, but mayalso be configured to generate a plurality of light beams 5.

Here, by way of example, the optical device 600 of FIG. 6a comprises adisplay device comprising a plurality of pixels 602 as light sources601. As explained further below, the invention relates specifically tothe use of the optical adjuster in an autostereoscopic display device.The adjuster 1 is configured to adjust the directions of the pluralityof light beams 5. The plurality of pixels 602 generate the plurality oflight beams 5, which may be manipulated by the adjuster 1. In a specificembodiment, the optical device 600 may optionally comprises a pluralityof adjusters 1.

In another embodiment, the optical device 600 is an illumination device,see FIG. 6b . Such illumination device may be a lamp, especially asubstantially point source lamp, such as a spot light. Hence, in anembodiment, the optical device 600 comprises a spot light as lightsource 601. Especially, the light source 601 is configured to generate alight beam 5 with an opening angle (2*θ) selected from the range of2-20°, such as preferably 2-10°. The adjusted beam (or adjusted lightbeam), downstream of the adjuster 1, when the adjuster 1 is switched on,is indicated with reference 5′.

FIG. 6c schematically depicts an embodiment of the optical device 600,wherein the device is arranged to detect light. The optical device 600comprises an optical sensor 651, such as a CCD array, and the adjuster 1as described herein. The adjuster may be used to redirect light beams 5in the direction of the optical sensor. For instance, in this way onemay scan or sweep areas.

The adjuster described above is for adjusting the direction of a lightbeam 5. The adjuster 1 has an off-state and on-state and comprises astack 10 of layers. The stack 10 comprises a first solid material layer100 having a first optic axis 111, a second solid material layer 200having a second optic axis 211, and switchable birefringent material 30.Further, the stack includes a first interface 130 between the firstsolid material layer 100 and birefringent material 30 and a secondinterface 230 between the second solid material layer 200 andbirefringent material 30. In the off-state, the birefringent material 30at the first interface 130 is configured to have an optic axis parallelto the first optic axis 111 and the birefringent material 30 at thesecond interface 230 is configured to have an optic axis parallel to thesecond optic axis 211. In the on-state, the birefringent material 30 atthe first interface 130 is configured to have an optic axisperpendicular to the first optic axis 111 and the birefringent material30 at the second interface 230 is configured to have an optic axisperpendicular to the second optic axis 211. This device may be used toredirect light beams, for instance for spot lights, display devices oroptical sensors.

The use of an adjuster has been described above in connection withdevices which are used to redirect optical beams such as spot lights orvehicle headlights. The invention relates specifically to the use ofthis type of adjuster applied to autostereoscopic display devices.

Autostereoscopic displays can be divided in two groups, one for whichglasses are required and one for which this is not required. For thelatter, the display sends out angle dependent images. The design is madesuch that the left and the right eye receive different images and a 3Dimpression is obtained.

Angle dependent images can be obtained from an LCD-TV with a specialbacklight or with a lenticular attached to the front of the display. Thelenticular comprises an array of cylinder lenses, and projects the LCpixel plane to infinity. In such cases, the lenses transform differencesin position to differences in angle. This means that only a selection ofpixels can be seen from a certain angle. More different views for moreangles leads to a better 3D impression. However, besides giving the 3Dimpression, more views also automatically reduce the resolution that isseen since all available pixels have been divided among the views: moreviews means less pixels per view. This leads to a trade-off betweenresolution and the number of views. A detailed description of one way toconstruct an autostereoscopic device in terms of design of a solidmaterial (non switchable) lenticular array is described in e.g. U.S.Pat. No. 6,064,424, the contents of which are incorporated by reference.Other ways of designing autostereoscopic display may be used.

A resolution loss may be acceptable for showing 3D content but fordisplaying 2D content (in which all the views are the same) it is oftennot acceptable. In order to overcome this issue, several so-called 2D/3Dswitchable displays have been proposed. These have a fixed lenticularstructure that is filled up with a birefringent liquid crystal. Byswitching the liquid crystal, the lenticular can be switched on and off.A more detailed description of the design and operation of such a deviceis found in e.g. U.S. Pat. No. 6,069,650, the contents of which areincorporated by reference. Especially the way for providing lensfunction or transparent function of the lenticular in relation to 2D or3D mode is described in detail. The described switchable principle inthe patent may require the light from the display to be polarized e.g.in case a regular LCD panel is used as the display panel. Such LCDpanels are known to provide polarized light in general.

The output of an OLED display is basically unpolarized. In order toapply standard switchable lenticulars, a polarizer is needed in thesystem for removing the light with the wrong polarization. This willreduce the light output by 50%, giving a loss in brightness or a loss inpower efficiency.

FIG. 7 shows how the switchable lenticular can control the light paths.The left figure shows no lens action while the right figure shows lensaction. The orientation of the LC is different in the two Figs. Sincethe light is polarized, it will encounter in the left figure theordinary index of refraction which is matched with the replica. Due tothis match, there is no lens action. In the right figure, the light willencounter the extra-ordinary index of refraction which is not matchedwith the replica, giving a lens action.

A problem with this system is that it can only be used for onepolarization of the light, making it unsuited for unpolarized OLEDdisplays.

The light adjuster described above can be used to provide a switchablelens function. The interfaces 130,230 become the lenticular lenssurfaces.

FIGS. 8 and 9 show a first example of implementation of a switchablelenticular arrangement suitable for an unpolarized display output (suchas an OLED display) and using the light redirection concept explainedabove.

FIG. 8 shows the system in the 2D mode. This corresponds to theconfiguration explained with reference to FIG. 2a , but with separateswitchable layers 30 a, 30 b and the two fixed layers 100, 200.

At the curved lens surfaces there is no difference in optical propertiesof the materials and therefore no lens action. This will give perfect 2Dimages.

FIG. 9 shows the system in the 3D mode. This corresponds to theconfiguration explained with reference to FIG. 2b , but again withseparate switchable layers 30 a, 30 b and the two fixed layers 100, 200.The medium in the middle has switched, and the lower layer 200 refractsone of the polarizations while the layer above 100 switches the otherpolarization.

The result is that even with an unpolarized light input, the lens actioncan be turned on and off.

FIGS. 10 and 11 show a first example of implementation of a switchablelenticular arrangement in accordance with the invention, suitable for anunpolarized display output (such as an OLED display) and using the lightredirection concept explained above.

FIG. 10 shows the system in the 2D mode. This corresponds even moreclosely to the configuration explained with reference to FIG. 2a , witha single switchable layer 30 and the two fixed layers 100, 200. Thisimplementation is easier to make from a fabrication point of view. Inaddition there will be less cross talk.

As described above, the single switchable layer 30 is filled with liquidcrystal which rotates the polarization over 90 degrees. Since theoptical properties are matched at the interface, no lens action willappear. This is the 2D mode.

FIG. 11 shows the system in the 3D mode. Since the liquid crystal isuntwisted in the cell, both polarizations will refract.

There are two potential problems with the design of FIGS. 10 and 11. Thefirst is that the thickness of the switchable LC layer is not wellcontrolled in the center of the lens arrangement. This can lead toartefacts in some circumstances. The second problem is that light goingthrough a certain lens-interface at the lower lenticular may go throughanother lens-interface at the lenticular above that is shifted by one ormore lenses. This leads to cross-talk which can be annoying. This isrepresented by arrow 1100.

In order to address this issue, the lenticulars can be placed very closeto each other such that the sides of the lenses almost touch each other.FIGS. 12 and 13 show a second example in accordance with the inventionusing this concept. In particular, the minimum spacing between thenon-switchable lenses is less than the depth of the lens (with referenceto FIG. 12, s<d). Preferably, the minimum spacing s is less than thedepth of the lenses of both arrays. The lenses of the two arraystypically have the same depth and pitch (as shown) but this is notessential. This reduction in spacing leads to a reduction of cross-talk.

FIG. 12 shows the 2D mode, and FIG. 13 shows the 3D mode.

In order to make this possible, there are some restrictions on thepossible combinations of optical materials. Birefringent materials areoften specified with Δn=nE−nO, where nE is the extra-ordinary index ofrefraction and nO is the ordinary index of refraction.

For the embodiment of FIGS. 12 and 13, the ordinary index and the extraordinary index of refraction of the three materials used (two fixedlenticulars and switchable LC) should all be the same. In addition, forthe lens shape shown the Δn should be negative as well (in order toprovide the bending towards the normal in the left part of FIG. 13 forexample).

The switching of the liquid crystal can be achieved by combining analignment layer, suitably positioned electrodes, and suitable type of LC(in particular the Δε property).

Alignment layers can for instance force the LC close to the boundary toorient itself with an angle to the boundary where this angle can forinstance be close to zero or 90 degrees. To provide LC alignment alongthe interface of the lenses, in-plane-switching electrodes can forexample be used. These methods are all well-known to those skilled inthe art.

The arrangement of layers can be interchanged in the designs above. Thetwo lens arrangements are shown with the same lens pitch, but these maybe different. The two fixed lens arrangements can also have differentangles if desired. The fixed lenticulars may also be homeotopicallyaligned

In the arrangement described above, two switchable lenticulars each acton perpendicular polarization components of the incident light. Thelenticulars are spaced by a switchable non-isotropic medium and thelenticulars themselves are non-isotropic having corresponding opticalrefractive index properties as the medium between them. This means thatboth polarizations can be used making the system efficient.

In the drawings, less relevant features like electrical cables, etc.have not (all) been drawn for the sake of clarity.

In the embodiments described above the adjuster is used to createmultiple views in such a way that autostereoscopic viewing is enabled.In one example this may be done by designing the lenticulars such thatindividual pixels of the display panel are projected into the differentviews. For the detailed description see the US patents referred to herebefore and the description of the current invention.

The adjuster of the current invention is however equally well suitablefor providing a dual-view display where multiple viewers can observedifferent 2D content. For example the driver/pilot andco-driver/co-pilot of a vehicle or aircraft may be provided by trafficdata and non-traffic data such as movie or other, respectively. Adetailed description of such displays is provided in e.g. internationalapplication PCT/IB03/03844, the content of which is incorporated byreference. The application provides dual view displays having parallaxbarriers or having lenticular arrays. Without having to repeat thecontent of that application, the description of the embodiments thatrelate to the display having a lenticular array in PCT/IB03/03844provide examples of how to construct a dual view display in terms ofrelations of pixel dimensions and lenticular design. In order to arriveat a dual view display of the current invention, the lenticular of thedisplay of PCT/IB03/03844 must be replaced with the adjuster of thecurrent invention where the dimensions of the adjuster lenticulars areto be chosen conform the description for the relevant embodiments of thedisplay of PCT/IB03/03844. Furthermore, the LCD display device may bereplaced with a display panel that provides substantially unpolarizedlight such as e.g. an OLED display panel.

The term “substantially” herein, such as in “substantially flat” or in“substantially consists”, etc., will be understood by the person skilledin the art. In embodiments the adjective substantially may be removed.Where applicable, the term “substantially” may also include embodimentswith “entirely”, “completely”, “all”, etc. Where applicable, the term“substantially” may also relate to 90% or higher, such as 95% or higher,especially 99% or higher, including 100%. The term “comprise” includesalso embodiments wherein the term “comprises” means “consists of”.

Furthermore, the terms first, second, third and the like in thedescription and in the claims, are used for distinguishing betweensimilar elements and not necessarily for describing a sequential orchronological order. It is to be understood that the terms so used areinterchangeable under appropriate circumstances and that the embodimentsof the invention described herein are capable of operation in othersequences than described or illustrated herein.

The devices herein are amongst others described during operation. Aswill be clear to the person skilled in the art, the invention is notlimited to methods of operation or devices in operation.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe able to design many alternative embodiments without departing fromthe scope of the appended claims. In the claims, any reference signsplaced between parentheses shall not be construed as limiting the claim.Use of the verb “to comprise” and its conjugations does not exclude thepresence of elements or steps other than those stated in a claim. Theterm “and/or” includes any and all combinations of one or more of theassociated listed items. The article “a” or “an” preceding an elementdoes not exclude the presence of a plurality of such elements. Thearticle “the” preceding an element does not exclude the presence of aplurality of such elements. The invention may be implemented by means ofhardware comprising several distinct elements, and by means of asuitably programmed computer. In the device claim enumerating severalmeans, several of these means may be embodied by one and the same itemof hardware. The mere fact that certain measures are recited in mutuallydifferent dependent claims does not indicate that a combination of thesemeasures cannot be used to advantage.

The invention claimed is:
 1. A multi-view display comprising: an arrayof pixels, wherein each pixel emits a light; a first layer disposed onthe multi-view display, wherein the first layer has a first opticalaxis; a second layer, wherein the second layer has a second opticalaxis; a first switchable birefringent material disposed between thefirst layer and the second layer, wherein the first birefringentmaterial has a first state and a second state; a second switchablebirefringent material disposed between the first switchable birefringentmaterial and the second layer, wherein the second birefringent materialhas a third state and a fourth state; a first interface between thefirst layer and the first switchable birefringent material, wherein thefirst interface defines a first array of lenticular lenses, the firstarray of lenticular lenses having a first depth; and a second interfacebetween the second layer and the second switchable birefringent materialwherein the second interface defines a second array of lenticularlenses, the second array of lenticular lenses having a second depth,wherein in the first state, the first switchable birefringent materialis arranged to have a first birefringent optical axis parallel to thefirst optical axis, wherein in the third state the second switchablebirefringent material is arranged to have a second birefringent opticalaxis parallel to the second optical axis, wherein in the second state,the first switchable birefringent material is arranged to have the firstbirefringent optical axis perpendicular to the first optical axis,wherein in the fourth state the second switchable birefringent materialat the second interface is arranged to have the second birefringentoptical axis perpendicular to the second optical axis, wherein a spacingbetween the first layer and the second layer is less than the firstdepth and is less than the second depth.
 2. The multi-view display ofclaim 1, wherein the first optical axis and the second optical axis areperpendicular to each other.
 3. The multi-view display of claim 1,wherein in the second state the first birefringent axis is arranged tobe parallel to the second birefringent optical axis in the fourth state.4. The multi-view display of claim 1, wherein the light comprisesunpolarized light.
 5. The multi-view display of claim 1, wherein thepixels comprise organic light emitting diodes.
 6. The multi-view displayof claim 1, wherein the pixels comprise light emitting diodes.
 7. Themulti-view display of claim 1, wherein the first state configures themulti-view display as a two-dimensional display, wherein the secondstate configures multi-view display as a three-dimensionalautostereoscopic display.
 8. The multi-view display of claim 1, whereinthe first state configures the multi-view display device as a singleview display, wherein the second state configures the multi-view displaydevice as a multi-view display.
 9. The multi-view display of claim 1,wherein the first switchable birefringent material is a twisted nematicliquid crystal material.
 10. The multi-view display of claim 1, whereinthe first switchable birefringent material is a chiral nematic liquidcrystal material.
 11. A multi-view display comprising: a display panel,the display panel having pixels, the pixels arranged for generatinglight beams; and an adjuster, wherein the adjuster is arranged foradjusting a direction of the light beams, wherein the adjuster has anoff-state and an on-state, the adjuster comprising: a first layer havinga first optical axis; a second layer having a second optical axis; afirst switchable birefringent material disposed between the first layerand the second layer, wherein the first birefringent material has afirst state and a second state; a second switchable birefringentmaterial disposed between the first switchable birefringent material andthe second layer, wherein the second birefringent material has a thirdstate and a fourth state; a first interface between the first layer andthe first switchable birefringent material, wherein the first interfacedefines a first array of lenticular lenses, the first array oflenticular lenses having a first depth; and a second interface betweenthe second layer and the second switchable birefringent material whereinthe second interface defines a second array of lenticular lenses, thesecond array of lenticular lenses having a second depth, wherein thefirst array of lenticular lenses and the second array of lenticularlenses are arranged to adjust the direction of the light beams, whereinin the off-state, the first switchable birefringent material isconfigured to have a first switchable birefringent optical axis parallelto the first optical axis, wherein in the off-state and the secondswitchable birefringent material is configured to have a secondswitchable birefringent optical axis parallel to the second opticalaxis; wherein in the on-state, the first switchable birefringentmaterial is configured to have the first switchable birefringent opticalaxis perpendicular to the first optical axis, wherein in the on-statethe second birefringent material is configured to have the secondswitchable birefringent optical axis perpendicular to the second opticalaxis.
 12. The multi-view display of claim 11, wherein the first opticalaxis and the second optical axis are perpendicular to each other. 13.The multi-view display of claim 11, wherein in the second state thefirst switchable birefringent axis is arranged to be parallel to thesecond switchable birefringent optical axis in the fourth state.
 14. Themulti-view display of claim 11, wherein the light beams comprisesunpolarized light.
 15. The multi-view display of claim 11, wherein thepixels comprise organic light emitting diodes.
 16. The multi-viewdisplay of claim 11, wherein the pixels comprise light emitting diodes.17. The multi-view display of claim 11, wherein the off-state configuresthe multi-view display as a two-dimensional display, wherein theon-state configures multi-view display as a three-dimensionalautostereoscopic display.
 18. The multi-view display of claim 11,wherein the off-state configures the multi-view display device as asingle view display, wherein the on-state configures the multi-viewdisplay device as a multi-view display.
 19. The multi-view display ofclaim 11, wherein the switchable birefringent material is a twistednematic liquid crystal material.
 20. The multi-view display of claim 11,wherein the switchable birefringent material is a chiral nematic liquidcrystal material.